In a letter to Vulcan's board today, Martin Marietta said the proposed combination is a "compelling value-enhancing opportunity." It made the letter public in a statement sent through Business Wire.

Martin Marietta announced a hostile takeover for Vulcan in an all-stock transaction valued on Dec. 12 at about $4.7 billion. The offer is being made directly to investors after Vulcan, the largest U.S. producer of crushed stone, broke off talks on a combination, Martin Marietta has said.

"Statements in Vulcan's New Jersey court papers that our proposal is an attempt 'to snatch Vulcan for the lowest possible price,' ... are simply inaccurate," Martin Marietta CEO Ward Nye wrote in the letter.

Nye also writes he was concerned the papers imply the transaction has been rejected, even though Vulcan's board has yet to publicly state its position on the proposal.

Martin Marietta is offering 0.5 shares for each share of Vulcan.

The offer follows losses for Vulcan in three of the past four quarters amid a U.S. construction recession.